Effect of Quebracho tannin extract on soybean and linseed oil biohydrogenation by solid associated bacteria: an in vitro study

An in vitro trial was carried out to study the effects of Quebracho tannins extract (QE) on fatty acid profile of rumen solid adherent bac- teria (SAB) during the fermentation of diets supplemented with soybean or linseed oil, as sources of linoleic (LA; 18:2 n-6) and α- linolenic acid (α-LNA; 18:3 n-3), respectively. Two control diets were prepared using a basal mixture of grass hay [760 g/kg on dry matter (DM)], soybean meal (55 g/kg DM), barley meal (130 g/kg DM), vitamin mineral premix (20 g/kg DM) and 35 g/kg DM of soybean (SOC diet) or linseed oil (LOC diet) as lipid supple- ment. Other two diets (SOCT and LOCT) were obtained by integrating SOC and LOC with QE (49 g/kg DM). The results confirmed that Quebracho tannins may be an effective method for reducing in SAB the biohydrogena- tion of LA (17.3 vs 34.5 g/100 g of fatty acid in SOC and SOCT, respectively) and LNA (10.7 vs 21.4 g/100 g of fatty acid in LOC and LOCT, respectively), but not for increasing the rumen accumulation of cis9, trans11 18:2 (0.77 vs 0.32 g/100 g of fatty acid in SOC and SOCT, respec- tively; 0.51 vs 0.43 g/100 g of fatty acid in LOC and LOCT, respectively) and trans11 18:1 (6.15 vs 3.64 g/100 g of fatty acid in SOC and SOCT, respectively; 5.53 vs 4.47 g/100 g of fatty acid in LOC and LOCT, respectively).